Telephone system



No. 626,462. Patented June 6, I899.

W. D; GHARKY.

TELEPHONE SYSTEM.

(Application fllad Dec. 24, isms.

(No Model.)

UNITED STATES PATENT OFFICE.

WVILLIAM D. GHARKY, OF PHILADELPHIA, PENNSYLVANIA.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 626,462, dated June 6, 1899.

Application filed December 24, 1898. Serial No. 700,199. N model.)

To ctZZ whom it 71mg concern:

Be it known that 1, WILLIAM D. GHARKY, a citizen of the United States, residing in the city and county of Philadelphia, State of Pennsylvania,have invented certain Improvementsin Telephone Systems, of which the following is a specification.

My invention relates to telephone systems, and particularly to the arrangement and operation of what are known as multiple-station or many-party lines.

It has for its object the provision of improved means whereby a nu mber or all of the stations on any line may send and receive signals to and from each other and to and from a central office, the signaling-circuits being separate and distinct from the metallic talking-circuits in part orin whole, yet requiring only the usual pair of wires for their operation.

In another application filed concurrently herewith, Serial No. 700,200, I have illlustrated and described an arrangement similar in principle to that hereinafter set forth; but in that case the connections and arrangement are such that the central station only can call the substations, while the substations can call central,butnot each other. The present application is not concerned with such a construction specifically, although, broadly speaking, it is covered by the claims in the other case.

Stated generally, m y present invention contemplates the provision of a bridge or bridges across the metallic circuit which may or may not constitute a portion of the subscribers ordinary apparatus. These bridges contain more or less impedance-such, for instance, as properly-wound coils having closed .magnetic circuits-but preferably the bridges include parts of the ordinary talking apparatus, such as the secondary winding of the induction-coil. In any case the middle point of each bridge in an inductive sense is connected to ground through proper signaling apparatus. Thus if there are a number of stations on the same metalliccircuit any one. of them may call the others, and even if conversation is going on no substantialinterruption thereof will take place. The arrangement has many advantages besides this which scarcely need mention. Induced currents or static effects will be dissipated Without affecting any talk ing apparatus, while the multiplied conductivity of the line for signaling-current enables m ore subscribers to be thus grouped than would be possible with a series arrangement of the line-wires.

The accompanying drawings illustrate my invention, the same letters and figures of reference therein referring to the same parts throughout.

In the drawings, Figure 1 isa diagram showing a two-station arrangement only, it being understood that these stations stand for a much larger number. Figs. 2, 3, and 4 are diagrams of slightly-modified substation-circuits.

Referring to Fig. 1, X and Y are two s ub scribers stations having in common the linewires 1 and 2. It will be understood that in practice there will be anywhere from two to twenty or more substations like these connected to the same circuit; but for the purposes of illustration it is sufficient to show these two, as the others would all be duplicates thereof. R at station X is an ordinary telephone-receiver, included in a bridge 3 3 between the two line-wires 1 and 2. I is the secondary winding of an induction-coil, simi larly included in a bridge 4: 4:. From the middle point of this secondary winding a wire 6 is taken off and conducted to the ringer Q,

then to the generator G, and thence to ground.

5 designates the local circuit, containing the transmitter, the primary winding 1 of the induction-coil, the hook-switch H, and the battery Z). The generator is preferably provided with the usual push button or automatic shunt, which while it is not being operated vir' tually removes its resistance and impedance from the line. We thus have in a long line of, say, thirty substations, such as a country toll-line, a'signaling-circuit of only one-quarter the total resistance of the metallic circuit, together with the full complement of ringers, all in parallel with each other and all responsive, of course, to any sigimling-current passing along the line. A very great advantage in this arrangement over the ordinary bridging bell systems resides in the fact that it is not necessary to wind the ringers for Their resistance may vary high impedance.

7 generator in separate ground-taps, the ringer beingincluded in the wire 6-, leading out from the inductively central point of the induction-coil I, while the generator is included in a wire 7, leading out to ground from the midnaling instruments.

dle point of the windings of the receiver R.

In Fig. 3 I have shown both the ringer and the generator in the wire 7 from the middle point of the receiver-windings, while in Fig. 4 theground-wire 7 leads from the middle point of the secondary winding I, and two receivers are included in the samebridge with the secondary for the purpose of obtaining a balance.

Many other arrangements might be suggested which would give the desired results. Thus I might connect an ordinary impedance-coil, as shown at the right of Fig. 4, across the line-wires 1 and 2 and ground the middle point of its windings through the sig- I prefer, however, to have as few bridges across the metallic circuit as possible, inasmuch as each bridge adds another path, however limited, for leakage of voice-currents.

I am aware that it is not new to utilize the two sides of a metallic circuit in parallel for signaling, nor is it new to utilize the coils of working apparatus in a differential as well as a cumulat ve relation. I do not, therefore,

claim such arrangements broadly, but I believe that it is original with me to provide parallel signaling branches at a' number of stations in connection with a main circuit utilized in this manner.

What I claim, and desire to secure by Letters Patent of the United States, is

1. A multiple-station telephone-circuitcomposed of two conductors adapted to be used incommon by all the stations for talking purposes, telephones at all the stations adapted to be connected to the two conductors, a generator of signaling-current and a ringer, at each station, connected on one side to both conductors through bridged impedance, and on the other side to ground, substantially as described.

2. A multiple-station metallic telephonecircuit having coils of high impedance bridged across the metallic circuit at the various sta tions, conductors connecting the inductively middle points of said bridges with the ground, signal-receiving devices normally included in said groimdponductors, and generators of signaling-current adapted to be also included in said ground-conductors, substantially as described.

3. A multiple-station metallic telephonecircuit having at each station two bridges containing impedance, and a conductor connecting the inductively middle point of each of said bridges with the ground, a signal-receiving instrument connected to respond to current in one of said ground-conductors, and a generator arranged to send signaling-cur rent through the otherof said ground-conductors to the line, substantially as described.

In testimony whereof I have hereunto set my hand this 21st day of December, 1898.

WM; D. GHARKY.

Witnesses:

EDWARD E. CLEMENT,

CLAYTON McELRoY. 

